The present invention relates to methods of inducing immunological tolerance. More particularly, the present invention relates to the use of transplantation of allogeneic donor bone marrow cells (BMCs) to a restricted hematopoietic space of a sublethally conditioned host recipient to induce donor specific immunological tolerance in the host.
Transplantation of allogeneic donor cells, tissues or organs is central to the therapy of a large number of highly debilitating and/or lethal diseases, including many diseases for which such transplantation is the sole or highly preferred therapeutic option. For example, in the United States more than 19,000 transplants, half of the world total, are performed each year to treat many diseases collectively involving various tissues, including all major organs. The list of successfully transplanted cells, tissues and organs includes: kidney, heart, lung, liver, corneas, pancreas, pancreatic islets of Langerhans, intestines, brain tissue, liver, spleen, thymus, lymph nodes, bone marrow, skin, and bones. Combinations of tissue have also been transplanted, for example, bone marrow-solid organ transplants, heart-lung transplants, pancreas-kidney transplants, and pancreas-kidney-intestinal transplants.
Among the diseases which can be treated by bone marrow transplantation (BMT), are more than 20 otherwise fatal diseases that include the six or seven genetically different forms of severe combined immunodeficiency (SCID), various forms of congenital or genetically determined hematopoietic abnormalities, combinations of these two, certain anemias, osteopetrosis, a variety of high risk leukemias and several forms of severe life-threatening aplastic anemia. These diseases include severe combined immunodeficiency (SCID) autosomal recessive with and without B cells [no adenosine deaminase (ADA) deficiency]; SCID X-linked recessive without B cells; SCID autosomal recessive with ADA deficiency; Wiskott-Aldrich syndrome; Blackfan-Diamond syndrome; Fanconi anemia; severe neutrophil dysfunction; chronic granulomatous disease of childhood; severe (Kostman-type) agranulocytosis; immunodeficiency and neutropenia of cartilage-hair hypoplasia; infantile and late onset osteopetrosis; aplastic anemia-toxic chemical, idiopathic, immunological, and genetic (non-Fanconi); acute myeloid leukemia; chronic myeloid leukemia; Burkitt lymphoma, and recurrent acute lymphatic leukemia. Other diseases that have been treated recently with BMT include metabolic storage diseases such as Gaucher's disease, hemoglobinophaties such as thalassemia, and even some solid tumors such as neuroblastoma.
Autoimmune diseases have also come to be regarded as stem cell disorders in recent years and treatment of various autoimmune diseases by BMT is a focus of attention today (Ikehara S., 1998. Int J Mol Med. 1:5–16).
Transplantation of allogeneic cells, tissues and organs has the potential to treat the large numbers of patients who do not receive such therapy since, for example, in the United States more than 200,000 people suffer from kidney failure at any one time, and more 60,000 people die of liver failure yearly.
Due to the chronic shortage of compatible donors, each year more than 56,000 critically ill people in the United States are on waiting lists to receive an organ transplant that could prevent further death or disability.
However, transplantation of allogeneic cells, tissues or organs involves significant drawbacks for which no adequate solutions exist. Such drawbacks, including graft rejection, complications from immunosuppressive therapy and graft-versus-host disease, frequently occur, and are frequently highly debilitating or lethal.
All individuals express unique combinations of cell surface molecules, termed major histocompatibility antigens, which function to enable the immune system to distinguish self from non-self, and to thereby trigger immunological elimination of foreign tissues. Thus, transplantation therapies are burdened by the need to select transplant donors whose major histocompatibility antigens are as genetically close to those of the recipient as possible and by the mandatory requirement for life-long administration of potent immunosuppressive agents, such as cyclosporin, to combat graft rejection and graft-versus-host disease in transplant recipients.
Graft rejection may occur through a number of different mechanisms, with the time course of rejection being characteristic of the particular mechanism. Early rejection (hyperacute rejection) occurring within minutes or hours of transplantation, involves complement activation by components that are present at time of the transplant operation. Activation may occur via the classical pathway by preformed antibodies that are reactive with the “foreign” or non-self markers of the graft or via the alternative pathway in response to tissue damage in the graft as a result of, for example, ischemic damage to the organ during storage before transplantation. Acute rejection occurs days to weeks after transplantation, and is caused by sensitization of the host to the foreign tissue that makes up the graft. Once the host's immune system has identified the transplanted tissue as foreign, all the resources of the immune system are marshalled against the graft, including both specific (e.g., B-cell, and T-cell dependent) responses and non-specific (phagocytic, complement-dependent, etc.) responses. In cases where the graft recipient is immunosuppressed, chronic graft rejection, a T cell mediated process, will eventually occur within a number of years. In chronic graft rejection, the graft may survive long enough for tissue to undergo changes which ultimately affect survival of the graft. Such changes include hyperplasia, tissue hypertrophy, and endothelial cell damage leading to narrowing of the vascular lumen, potentially impairing the oxygen supply to the graft tissue. Rejected transplants must be surgically removed, and if the transplant is a life-sustaining organ such as a lung, liver, or heart, a patient may die before a replacement organ is found.
Although the standard use of immunosuppressive agents such as cyclosporin has greatly increased the short-term success rate, notably of transplants of solid organs such as kidney, and renders allogeneic transplantation practicable, such drugs display pronounced side-effects, such as dramatically increasing the risks of cardiovascular disease, potentially lethal opportunistic infections and malignancies. Furthermore, as described hereinabove chronic rejection sooner or later remains inevitable under current transplantation/immunosuppression regimens. Moreover, immunosuppressive drugs have not had a significant effect on long-term transplant survival. More than half of transplanted kidneys, the organ most often transplanted, are rejected within ten years, and the patient must receive another kidney transplant or start dialysis treatments, which are uncomfortable, expensive, and time-consuming.
Similarly to solid organ transplants, widespread clinical application of bone marrow transplantation (BMT) as a means of tolerance induction is restricted by the high morbidity and mortality rates associated with toxicity of conditioning, graft-versus-host disease and failure of engraftment (Armitage J O., 1994. New Engl J Med. 330:827).
Thus, because of the toxicity and incomplete response rate to conventional treatment of donor tissue rejection, alternative approaches are needed to induce immunological tolerance to allografts. Tolerance is the acquired lack of specific responsiveness to an antigen to which an immune response would normally occur. Typically, to induce tolerance, there must be an exposure to a tolerizing antigen, which results in the death or functional inactivation of certain lymphocytes. Complete tolerance is characterized by the lack of a detectable immune response to a repeat antigenic challenge, and partial tolerance is typified by a quantitative or qualitative reduction of an immune response.
One potentially promising strategy which has been employed to induce allogeneic donor specific immunological tolerance in a host without, or with reduced, life-long immunosuppressive drug regimens involves transplantation of donor bone marrow cells (BMCs) in the host. Establishment of donor specific hemopoietic chimerism in the host following such transplantation has been shown to correlate with tolerance of the host to subsequent donor derived grafts, including organ grafts (Ildstad S T. and Sachs D H., 1984. Nature 307:168; Ildstad S T. et al., 1985. J Exp Med. 162:231; Sharabi Y. and Sachs D., 1989. J Exp Med. 169:493; Markus P M. et al., 1993. Cell Transplant. 2:345). transplanted BMCs
However, such an approach of inducing donor specific immunological tolerance in a host presents significant drawbacks. The lethal conditioning regimens, such as myoablative total body irradiation, required to ensure stable engraftment of allogeneic donor BMCs in the host are unacceptably dangerous, being often lethal or highly toxic; the efficiency of establishment of donor specific hemopoietic chimerism is highly inefficient; and such transplantation of allogeneic BMCs is associated with unacceptably high rates of graft-versus-host disease.
Various prior art approaches have been attempted for induction of donor specific immunological tolerance in a host via allogeneic donor BMC transplantation.
One approach has used high levels of whole body irradiation (1.5–3 Gy) to condition murine hosts prior to syngeneic donor BMC transplantation in attempt to facilitate donor specific hemopoietic chimerism. However, only about 50% of animals conditioned with 1.5 Gy WBI showed evidence for BMC engraftment (Tomita Y. et al., 1994. Blood 83:939).
Another approach has utilized whole body irradiation of at least 0.5–0.6 Gy to condition murine hosts prior to MHC-mismatched allogeneic donor BMC transplantation for induction of tolerance to subsequent donor type skin grafts. However, the level of donor chimerism achieved in these studies was less than 50% (Colson Y L. et al., 1995. J Immunol. 155:4179).
Yet another approach has utilized lethal whole body irradiation, to condition rat hosts prior to allogeneic donor BMC transplantation for induction of tolerance to subsequent donor type cardiac grafts. In this approach, however, only thirty-seven percent of animals displayed stable hemopoietic chimerism (Markus P M. et al., 1993. Cell Transplant. 2:345).
Still another approach has employed supralethal conditioning of rat hosts prior to allogeneic+ syngeneic donor T cell depleted BMC transplantation for induction of tolerance to subsequent donor type skin or cardiac grafts (Colson Y. et al., 1995. Transplantation 60:971).
Yet still another approach has used 0.3 Gy whole body irradiation and administration of anti-lymphocyte globulin and cyclophosphamide to condition murine hosts prior to allogeneic donor BMC transplantation for induction of tolerance to subsequent donor type skin grafts (Colson Y. et al., 1996. J Immunol. 157:2820).
A further approach has utilized 3 Gy whole body irradiation and administration of anti-T cell monoclonal antibodies to condition murine hosts prior to allogeneic donor BMC transplantation for induction of tolerance to subsequent donor type skin grafts (Tomita Y. et al., 1996. Transplantation 61:469).
Yet a further approach has employed administration of CTLA4-Ig to condition murine hosts prior to allogeneic donor BMC transplantation for induction of tolerance to subsequent donor type skin or cardiac grafts (Pearson T C. et al., 1996. Transplantation 61:997). Such inhibition of costimulatory pathways, however did not induce optimal long-term tolerance to the secondary organ grafts, and the immune suppression was not donor specific.
Still a further approach has employed anti-CD4 and anti-CD8 mAbs, 300-rad whole body irradiation, and 700-rad thymic irradiation to condition murine hosts prior to allogeneic donor BMC transplantation for induction of tolerance to subsequent donor type skin grafts (Sharabi Y. and Sachs D., 1989. J Exp Med. 169:493).
Yet still a further approach has utilized 5.5 Gy whole body irradiation to condition murine hosts prior to transplantation of allogeneic donor BMCs via portal vein injection for treatment of autoimmune disease (Kushida T. et al., 2000. Blood 95:1862).
An additional approach has employed 5.5 Gy whole body irradiation to condition murine hosts prior to transplantation of allogeneic donor BMCs via intra-bone marrow (IB) injection for treatment of autoimmune disease (Kushida T. et al., 2001. Blood 97:3292).
Yet an additional approach has used intra-osseous injection of allogeneic bone marrow in patients receiving marrow transplants from HLA-identical or one antigen-mismatched related donors (Hagglund H. et al., 1998. Bone Marrow Transplantation 21:331). In these trials, however, haematopoietic recovery was not improved relative to intravenous bone marrow administration.
Still an additional approach has utilized 6.5 Gy whole body irradiation to condition murine hosts prior to transplantation of a megadose of allogeneic donor BMCs for induction of donor specific hemopoietic chimerism (Bachar-Lustig B et al., 1995. Nat Med 1:1268).
Yet still an additional approach has employed transplantation of a megadose of allogeneic donor stem cells via intravenous injection for induction of donor specific hemopoietic chimerism in mice (Gandy K L and Weissman I L. 1998. Transplantation 65:295).
Another approach has used 0.5 Gy whole body irradiation, tacrolimus and anti lymphocyte serum to condition murine hosts prior to transplantation of a megadose of allogeneic donor BMCs for induction of tolerance to subsequent donor type cardiac grafts (Sykes M. et al., 1997. Nat Med. 3:783).
Yet another approach has used transplantation of megadoses of c-Kit+Thy−1.1(lo)Lin−/loSca−1+allogeneic donor BMCs for induction of donor specific hemopoietic chimerism in mice (Uchida N. et al., 1998. J Clin Invest. 101:961).
Yet another approach has utilized transplantation of megadoses of allogeneic donor Scal+Lin− BMCs in attempts to induce tolerance to subsequent donor type skin grafts (Reisner Y. and Martelli M F., 2000. Exp Hematol. 28:119).
However, all of the aforementioned approaches suffer from significant disadvantages. All prior art approaches have either employed BMC megadoses in mice which cannot be practically achieved in humans; have not shown efficient engraftment of transplanted cells, tissues or organs; have not shown satisfactory long-term survival of BMC and/or secondary organ grafts; have employed harmful whole body irradiation; have employed lethal or supralethal conditioning regimens; have employed toxic drugs for conditioning; have employed inefficient intravenous injection for delivery of BMCs; have not addressed issues of donor specific hemopoietic chimerism and/or tolerance to secondary donor organ grafts; have not demonstrated the capacity to induce immunological tolerance to different donor type secondary organ grafts; have not demonstrated the capacity to induce tolerance to a solid graft administered simultaneously with a tolerogenic dose of BMCs; and/or have resulted in unacceptable rates of graft-versus-host disease.
Thus, all prior art approaches have failed to provide an adequate solution for safely, effectively, and flexibly inducing allogeneic donor specific immunological tolerance via administration of donor-derived BMCs.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method of inducing immunological tolerance devoid of the above limitation.